I think it depends on what people's definition of ukemi is. If by ukemi you mean taking falls, then I agree... yes, that sort of ukemi has no bearing on kokyu or development of kokyu. You might "get" some, but there are other, better ways of achieving it.

However, if you mean ukemi in the true sense of the word uke (receiving [with the]) mi (body).... then it changes the entire focus of what ukemi is.